mobile-config-firefox

Mobile and privacy friendly configuration for Firefox >= 91.

This does not replace a proper implementation in Firefox upstream (interesting stuff happens in issues linked in "References").

What this config does

• Adapt UI elements and "about:" pages to small screen sizes (when opened on small screen)
• Enable mobile gestures
• User agent set to same as Tor Browser for Android
• Privacy tweaks:
  • Disable search suggestions
  • Disable Firefox studies
  • Disable Telemetry
  • Set DuckDuckGo as default search engine, remove other search engines except for Wikipedia (only works in Firefox ESR, limitation of policies.json)
  • Install uBlock origin by default
• Uncluttering:
  • Disable built-in advertisements (e.g. hardcoded links for certain social media sites on the start page)
  • Disable "User Messaging" about new features etc.

For users: making changes

As user, it is possible to override all options set by this project. Usually it can be done in the preferences (which are now adaptive, so you can actually use them on your phone).

If it cannot be changed in preferences, look in /etc/firefox/policies/policies.json. You can see the active policies while Firefox is running in about:policies. The uBlock origin add-on for example, is getting installed through policies.json and can be removed in that file if you do not want it. Without editing the file, it can only be disabled in the add-on settings, and not removed, this is a limitation of policies.json.

Feel free to create an issue if you run into problems. Or even better, attempt to fix the problem yourself (see development instructions below) and submit a merge request.

Contributing changes to userChrome

Firefox' developer tools include a remote debugger, which even has the "pick an element" feature. You will be able to click that button on your PC, then tap on an element of the Firefox UI on your phone, and then you will see the HTML code and CSS properties on your PC just as if it was a website. So this is highly recommended when contributing changes to userChrome.css.

• Connect your phone and your PC to the same network (Wi-Fi or USB network)
• On your phone, open Firefox and about:config:
  • Change devtools.chrome.enabled to true
  • Change devtools.debugger.remote-enabled to true
  • The debugger will only listen on localhost by default. If you know what you are doing, you may set devtools.debugger.force-local to false, so it listens on all interfaces. Otherwise you'll need something like an SSH tunnel.
  • Close firefox
• Connect to your phone via SSH
  • Set up environment variables properly, so you can start programs (one lazy way to do it, is tmux on your phone in the terminal, then tmux a in SSH)
  • Run firefox --start-debugger-server 6000 (or another port if you desire)
• Run Firefox on your PC
  • Go to about:debugging
  • Add your phone as "network location"
  • Press the connect button on the left
  • If it does not work, check if a firewall on your phone is blocking the port (i.e. nftables in postmarketOS).
• On your phone
  • Confirm the connection on your phone's screen
    • If the button is not visible on the screen, try switching to a terminal virtual keyboard, hit "tab" three times and then return
• On your PC
  • Scroll down to Processes, Main Process, and click "Inspect"
  • Now use the "Pick an element" button as described in the introduction. Find the userChrome.css file in the "Style editor" tab and edit it as you like.
  • Consider copy pasting the contents to a text editor every now and then, so you don't lose it when closing Firefox by accident.

Note that after making changes to CSS files, and deploying them on your system (make install), you might need to restart firefox twice before changes are applied.

Coding guidelines

• Don't make longer lines than 79 columns where possible (like in PEP-8)
• Use 4 spaces for indent in all files, except for shell scripts (use tabs there). Consider configuring your editor to use .editorconfig, then it gets configured automatically.
• Linter: .ci/lint.sh (consider setting it as pre-commit hook, requires GNU grep)

Additional resources

• firefox-csshacks
• FirefoxCSS subreddit